Engine misfire linked to bad computer?

A little history....

2001 GA 3.4L SE. For about a year now I've had trouble with hard shifts to second, surging on inclines and slipping on hard exceleration that worsens as the engine/tranny heats up. I've had the PCM reflashed as suggested by the dealer, changed the plugs, and test driven twice with no results or chane.

Yesterday I finally had the car scanned for codes and it returned both P0440 and I believe P0300B. Now correct me if I'm wrong but P0440 is an EVAP Control System Malfuction while the other is either Multiple/Random engine misfires or just cylinder 2 misfire.

I was considering changing the coil packs and wires until something strange happened last night. I disconnected the battery to check and clean the connectors on the coil pack module just in case they were simply dirty. They're fine but when I started up the car afterwards is idled smoother and shifted better as well.

So now I'm wondering. If I disconnected the power it should have cleared any stored codes in the computer. Both after disconneting the battery and having the PCM flashed I have about and hour or trouble free driving.

Could a bad or faulty computer cause my misfire code to appear? Maybe my troubles with the tranny are related?

TIA.

sometimes simply disconnecting the battery and later reconnecting it will correct minor electronic gremlins but don't tell Xero this......:grinyes:

Well in my case the "gremlins" always return after an hour or so.

simply disconnecting the battery will not clear the codes. If you have trouble free driving until the engine heats up and you are getting a code for a specific cylinder check the coil specific to that cylinder. Sorry I don't have the resistance level handy but someone will post up what it is.

OK. What would cause the change in performance after disconnecting the power?

I heard that Jim :lol:

Misfire are either something in your ignition system as in coils/wires/plugs, then you can get misfires from injectors having shorts in the injector harness.
Bad injectors can cause a misfire too.

Though depending on your mileage you could also have trany troubles with the chugging, check out the thread titled this(if you havent already) it covers things on this problem.

Start simple and cheap :thumbsup:

Hello.
I am experiencing something similar to Brass GA. (Except the tranny issue) I have a 2003 GA 3.4L. The plugs and wires are about 9 months old. And they still look great, no cracks, etc. A few weeks ago the engine light came on and states misfire in cylinder two and coil pack. I have replaced the coil pack and put a new fuel injector in cylinder 2. The car is still misfiring. And the same codes for the coil pack and cylinder two misfire are still showing. Now with this being said, we are wondering too, if the computer has anything to do wth the misfire? We checked all of the wires for the fuel injectors, and they are all good. Any input would be greatly appreciated! Oh and I should add we did a compression test on cylinder 2, and it is normal.
Thank you.

Have you done a a coil output test on coil 2/5 with a spark tester? Test BOTH terminals...

Tried a noid light on cyl #2 injector harness connector?

Are you getting P0300 or P0302?

Have the lower/upper intake gaskets ever been replaced?

Faulty computers seem to be a pretty popular problem on Grand Ams. Electrical problems seem pretty common too. I would recommend checking the issues linked to the codes the computer is putting out, but there is a possibility the computer itself is going haywire.

We found out it wasn't the computer for the Grand Am. We found a broken wire near the wiring harness after we had changed the computer and it was still acting up. So now we have it temporarily fixed until I can find a wiring harness for the car.